1. Technical Field
This application relates to UMTS (Universal Mobile Telecommunications System) in general, and to a method and apparatus for controlling traffic volume measurement validity in a universal mobile telecommunications system in particular.
2. Description of the Related Art
UMTS is a third generation public land mobile telecommunication system. Various standardization bodies are known to publish and set standards for UMTS, each in their respective areas of competence. For instance, the 3GPP (Third Generation Partnership Project) has been known to publish and set standards for GSM (Global System for Mobile Communications) based UMTS, and the 3GPP2 (Third Generation Partnership Project 2) has been known to publish and set standards for CDMA (Code Division Multiple Access) based UMTS. Within the scope of a particular standardization body, specific partners publish and set standards in their respective areas.
Consider a wireless mobile device, generally referred to as user equipment (UE), that complies with the 3GPP specifications for the UMTS protocol. The 3GPP 25.331 specification, v.3.16.0, referred to herein as the 25.331 specification, addresses the subject of UMTS RRC (Radio Resource Control) protocol requirements between the UMTS Terrestrial Radio Access Network (UTRAN) and the UE.
Section 8.4 of the 25.331 specification provides that a UTRAN may control a measurement in the UE, by broadcast of SYSTEM INFORMATION and/or by transmitting a MEASUREMENT CONTROL message to the UE. The purpose of the measurement control procedure is to set up, modify or release a measurement in the UE.
A MEASUREMENT CONTROL message includes a measurement identity, a measurement command, for example, Setup, Modify or Release and a measurement type, specifying what the UE should measure. It may also include a variety of other control information depending on the measurement type. One of the possible measurement types is traffic volume measurement (TVM), which comprises measurements of uplink traffic volume. Control information for TVM includes measurement validity, which defines the UE states in which the measurement is valid.
The inventor has found that there is an inconsistency in the 25.331 specification relating to the validity of traffic volume measurements. As explained above, a traffic volume measurement is set up by the UTRAN sending a MEASUREMENT CONTROL message to the UE. This may include the optional information element (IE) ‘measurement validity’ and the IE ‘UE state’, which specifies the state in which the UE must be for the Traffic Volume Measurement to be valid. The ‘UE state’ may be one of ‘Cell_DCH’, ‘all states’ or ‘all states except Cell_DCH’
Traffic volume measurements are addressed at sections 8.4.1.3 and 8.4.1.6.6 of the 25.331 specification.
The relevant extract from section 8.4.1.3 specifies that:    “1> if the UE in CELL_FACH state receives a MEASUREMENT CONTROL message, which indicates the same measurement identity as that stored in the variable MEASUREMENT_IDENTITY:    2> update the stored information with the traffic volume measurement control information in variable MEASUREMENT_IDENTITY; and    2> refrain from updating the traffic volume measurement control information associated with this measurement identity in the variable MEASUREMENT_IDENTITY with the information received in System Information Block type 12 (or System Information Block type 11, according to subclause 8.1.1.6.11) until this measurement is explicitly released with another MEASUREMENT CONTROL message.”
The relevant extract from section 8.4.1.6.6 specifies that:
Upon transition from CELL_DCH to CELL_FACH or CELL_PCH or URA_PCH state, the UE shall:
    1> retrieve each set of measurement control information of measurement type “traffic volume” stored in the variable MEASUREMENT_IDENTITY; and    2> if the optional IE “measurement validity” for this measurement has not been included:    3> delete the measurement associated with the variable MEASUREMENT_IDENTITY.    2> if the IE “measurement validity” for the measurement has been included, and the IE “UE state” has been assign to value “CELL_DCH”:    3> stop measurement reporting;    3> store the measurement associated with the variable MEASUREMENT_IDENTITY to be used after the next transition to CELL_DCH state.    2> if the IE “measurement validity” for the measurement has been included, and the IE “UE state” has been assign to value “all states”:    3> continue measurement reporting.    2> if the IE “measurement validity” has been included and the IE “UE state” has been assigned to value “all s except CELL_DCH”:    3> resume this measurement and associated reporting.    1> if no traffic volume type measurement has been assigned to the UE with a MEASUREMENT CONTROL message that is valid in CELL_FACH or CELL_PCH or URA_PCH states (stored in the variable MEASUREMENT_IDENTITY), which has the same identity as the one indicated in the IE “Traffic volume measurement system information”:    2> store the measurement control information from the IE “Traffic volume measurement system information” received in System Information Block type 12 (or System Information Block type 11, according to subclause 8.1.1.6.11) in the variable MEASUREMENT_IDENTITY;    2> begin traffic volume measurement reporting according to the assigned information.”
Consider the scenario where the UE is in the Cell_FACH state and receives a MEASUREMENT CONTROL message to set up a traffic volume measurement with a validity of Cell_DCH. This means that the measurement will be stored in the variable MEASUREMENT_IDENTITY, so that the measurement can be set up when the UE moves to the Cell_DCH state. It should be noted that, according to section 8.4.1.3, the UE should not delete or overwrite this information unless the measurement has been explicitly released by another MEASUREMENT CONTROL message.
Now consider that the UE moves to Cell_DCH. The traffic volume measurement is then valid and so the measurements are made.
Now consider that the UE moves back to Cell_FACH. According to section 8.4.1.6.6, the measurement should be stopped, but the information retained in MEASUREMENT_IDENTITY for use on the next transition to Cell_DCH.
However, section 8.4.1.6.6 also states that if there is no measurement valid in Cell_FACH, then the one specified in System Information Block type 11 or 12 (SIB11 or SIB12) should be used.
If the TVM in SIB11/12 has the same identity as the TVM saved in MEASUREMENT_IDENTITY, that measurement would need to be updated, but this contradicts section 8.4.1.3 which states that this cannot be done until this measurement is explicitly released.